1. Field of the Invention:
The present invention relates to a floating seal device applicable to a drive wheel apparatus of a mining damp truck, or the like.
2. Description of the Prior Art:
At first, description will be made of a drive wheel apparatus of a mining damp truck in the prior art with reference to FIGS. 4 and 5. In FIG. 4, reference numeral 1 designates an axle case fixed to a vehicle body and having therein an electric motor, numerals 3 and 3' designate speed reduction gear devices, numeral 4 designates a wheel hub, numeral 5 designates a floating seal device, numeral 6 designates a bearing for rotatably supporting the above-mentioned wheel hub 4 on the axle casing 1, numeral 7 designates a drive wheel (tire) mounted to the above-described wheel hub 4, and provision is made such that when the electric motor is started rotation of the motor is transmitted via the speed reduction gear device 3 to the wheel hub 4' and thereby the drive wheel 7 is rotated. As shown in FIG. 5, the floating seal device 5 is composed of a fixed side seal retainer 20 fixed to the axle case 1, a rotary side seal retainer 23 fixed to the wheel hub 4, a fixed side O-ring 21 held by a tapered surface of the fixed side seal retainer 20, a rotary side O-ring 24 held by a tapered surface of the rotary side seal retainer 23, a fixed side seal ring 22 and a rotary side seal ring 25. The seal ring 22 on the fixed side (on the side of the axle case 1) and the seal ring 25 on the rotary side (on the side of the wheel hub 4) are resiliently pressed to each other by means of the respective O-rings 21 and 24 with their opposed surfaces 26 allowed to slide relative to each other, and thereby lubricant oil is sealingly closed within the reduction gear device (3 and 3'). When a recessed portion 27 provided in one part of the opposed surface 26 of the rotary side seal ring 25 is immersed in the lubricant oil within the reduction gear device 3, the lubricant oil within the reduction gear device 3 is led from the recessed portion 27 to between the opposed surfaces 26 sliding relative to each other due to capillary phenomena and forms an oil film, whereas when the above-mentioned recessed portion 27 is exposed from the lubricant oil within the speed reduction gear device 3, the lubricant oil sticking to the side walls of the recessed portion 27 is led from the side wall of the recessed portion 27 to between the opposed surfaces 26 sliding relative to each other due to centrifugal forces generated by rotation of the seal ring 25 and forms an oil film.
FIG. 6 shows another example of the floating seal devices in the prior art, in which a wedge-shaped recess is provided between a fixed side seal ring 28 and a rotary side seal ring 29 to thereby enhance the effect of introducing lubricant oil to between opposed surfaces 26 due to capillary phenomena.
In the floating seal device in the prior art shown in FIGS. 4 and 5, whether or not an oil film can be formed between the opposed surfaces 26 is dependent upon an immersed condition of the rotary side seal ring 25 in the lubricant oil. When the level of the lubricant oil within the reduction gear device 3 is low and hence the time when the rotary side seal ring 25 is not immersed is larger than the time of immersion thereof, the lubricant oil sticking to the side walls of the recessed portion 27 is the principal source of the lubricant oil fed to between the opposed surfaces 26. Thus, the amount of the fed oil is deficient, breakdown of the oil film occurs, hence the sliding opposed surfaces 26 become rough due to baking, and leakage of oil occurs. Whereas, if the level of the lubricant oil within the reduction gear device 3 is made high, then although the above-mentioned problem does not occur, the extent of the lubricant oil being stirred by rotary portions in the reduction gear device 3 becomes intense, and thus the loss of mechanical power is increased. In addition, as the amount of the lubricant oil stored within the reduction gear device 3 is increased, the weight of the device is increased, and moreover, there occurs the problem that replacement of the lubricant oil takes more time. The above-mentioned problems are also the same in the case of the prior art floating seal device shown in FIG. 6.